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1. Introduction
2. Fact or Fiction?
3. From Zygote to Newborn
4. Vulnerability during Prenatal Development
5. The Birth Process
6. The Newborn
7. Closing Thoughts
Introduction
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[Video: Prenatal Development and Birth Introduction]
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Fact or Fiction? Fiction Fact
1. An embryo is the developing human organism between the third and eighth week after conception.
2. By the end of the third month, the fetus has all of its body parts.
3. Teratogens are only a concern for women who use alcohol and drugs.
4. All newborn reflexes help a baby survive.
Beginning of
pregnancy
Pregnancy begins at conception, which is also the starting point of gestational age. However, the organism does not become an embryo until about two weeks later, and pregnancy does not affect the woman (and cannot be confirmed by blood or urine testing) until implantation.
Length of pregnancy
Full-term pregnancies last 266 days, or 38 weeks, or 9 months.
Trimesters
Instead of germinal period, embryonic period, and fetal period, some writers divide pregnancy into three-month periods called trimesters.
Due dateAlthough doctors assign a specific due date (based on the woman’s LMP), only 5% of babies are born on that exact date.
What is the timing and terminology of pregnancy?Popular and professional books use various phrases to segment pregnancy. The following comments may help to clarity the phrases used.
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How does implantation occur?
The First 14 Days implantation: The process beginning
about 10 days after conception, in which the developing organism nestles in, and attaches to the placenta that lines the uterus.
The Most Dangerous Journey
Two-celled stage
Zygote (single cell)
Fallopian tube
Ovary
Ovum
Ova
Sperm
Implantation
Conception
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Brain
Facial Features
External sex organs
Intestines
Arms, hands and fingers
As nerves and muscles form links to the brain, the embryo now moves spontaneously, as the brain begins to move muscles.
Eyes and eyelids are developed. Eyes will continue to migrate to the front of the head, where they will eventually rest. Eyelids begin to grow together and are only half closed. External, middle, and inner ears are now fully formed. External ears will continue to migrate to the side of the head, where they will eventually rest.
Urogenital membranes have developed into either male or female organs, and ovaries or testicles are visible. Clitoris or penis begins to form, but distinguishing the embryo’s sex is difficult.
The intestines begin to move from the umbilical cord to the embryo’s body cavity.
Arms are well formed, longer, and can bend at elbows and move forward. Fingers elongate and digits are fully separated. Each finger has three digits, and the thumb has two digits.
Overall appearance
The head is still disproportionately large but is erect and appears rounded. The neck is well defined. The tail will disappear by the end of this week. Cartilage begins to turn into bone. The ectoderm layer is replaced by the beginnings of skin. The body becomes evenly rounded, due to the growth in the abdomen.
Brain
Facial Features
External sex organs Overall
appearance
Arms, hands and fingers
Intestines
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What happens during the embryonic period of prenatal development?
From the Third Through the Eighth Week
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From the Third Through the Eighth Week
[Video: Germinal and Embryonic Periods]
fetus: A developing human organism from the start of the ninth week after conception until birth.
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What happens during the fetal period of prenatal development?
9 12 16 20 24 28 32 36 38
From the Ninth Week until Birth
9 weeks through 38 weeks
Brain stem
Hindbrain Neural tube(forms spinal cord)
Forebrain
(a) 25 days
Midbrain
Prenatal Growth of the Brain
How does the brain grow during the periods, or stages, of prenatal development?
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Prenatal Brain Development
(b) 50 days (c) 100 days
(d) 20 weeks
(e) 28 weeks
(f) 36 weeks (full term)
From the Ninth Week until Birth
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[Video: Brain Development Animation: Prenatal]
What percentage of zygotes make it through each prenatal period? The Germinal
Period
The Embryonic Period
The Fetal Period
Birth
At least 60 percent of all developing organisms fail to grow or implant properly and thus do not survive the germinal period. Most of these organisms are grossly abnormal.
About 20 percent of all embryos are aborted spontaneously*, most often because of chromosomal abnormalities.
About 5 percent of all fetuses are aborted spontaneously before viability at 22 weeks or are stillborn, defined as born dead after 22 weeks.
About 31 percent of all zygotes grow and survive to become living newborn babies.
*Spontaneous abortions are also called miscarriages. This table does not include
induced abortions.Sources: Bentley & Mascie-Taylor, 2000; K.L. Moore & Persaud, 2003.
Making it to Birth
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What are the risks at different stages of development?Birth Defects from Teratogens: Time of Exposure and Effect on Major Organs
Germinal Period Main Embryonic Period (in weeks) Fetal Period (in weeks)
Central nervous system
Heart
Arms
Legs
Lips
Ears
Eyes
Teeth
Palate
Sex organs
Teratogens oftenprevent implantation
Common site(s)of action of teratogens
Highly criticalperiod
Less criticalperiod
Neural-tube defects
Mental retardation
Learning disabilities
Cleft lip
Low-set malformed ears and deafness
Cataract, glaucoma
Enamel staining
Cleft palate
Masculinization of female genitalia
Major congenital anomalies Functional defects and minor anomalies
1 2 3 4 5 6 7 8 9 16 32 38
Source: Adapted from K.L. Moore & Persaud. 2003 13
What are some prenatal tests?
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Benefits of Prenatal Care
Benefits of Prenatal Care
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[Video: Sonogram]
How do you feel about viewing the birth process?
1. A close friend or relative asks you to be present during the labor and at the birth of her child. You feel like saying:Yes, I want to be there!Yes, if you need me.Maybe; let me think about it.It’s something I don’t think I can do.Don’t know; it’s hard to imagine.
2. You learn that someone took a photograph of the moment of your birth. Are you:Very eager to see the photograph?Interested in seeing the photograph at some time?Turned off by the thought of the photograph?Both interested and turned off by the idea of the photograph?Don’t know.3. You learn that your class is scheduled to see a film of a birth. Are you:Very interested in seeing the film?Somewhat interested in seeing the film?Somewhat uneasy about seeing the film?Very uneasy about seeing the film?Both interested and uneasy?
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[Video: Birth]
apgar scale: A quick assessment of a newborn’s health, given twice (at one minute and five minutes after birth).
How is a Newborn tested?
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First Minutes and Complications
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First Minutes and Complications
[Video: Apgar Test]
Low Birth Weight (LBW): A body weight at birth of less than 5 ½ pounds (2,500 grams).
Very Low Birth Weight (VLBW): A body weight at birth of less than 3 pounds, 5 ounces (1,500 grams).
Extremely Low Birth Weight (ELBW): A body weight at birth of less than 2 pounds, 3 ounces; (1,000 grams). Why is birth
weight important?
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Variations in Birth Weight
Lagging physical and cognitive development confronts babies born early (or preterm, once called premature), and a preterm baby also is probably low birth weight.
Play video:An Observation of Premature Infants Clip F
Play video:An Observation of Premature Infants Clip E
Play video:Low Birth weight in India
reflex: An unlearned, involuntary action or movement in response to a stimulus.
What are some newborn reflex experiences?
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Variations in Birth
Breathing reflexes
Sucking reflexes Stepping reflexes Moro reflexes
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Reflexes
[Video: Newborn Reflexes]
What is a father’s role?
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Social Support
couvade: Symptoms of pregnancy and birth experienced by fathers.
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Social Support
[Video: The Experience of Pregnancy: The First Trimester]
From what you discovered about prenatal development in these slides, what examples can you cite to support the statement, “The most dramatic and extensive transformation of the entire life span occurs before birth?”
Closing Thoughts
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